The translation of modulated signals between different carrier frequencies is common in signal transmission. For example, upconverters are used in the television industry to translate information that is present at a particular low intermediate frequency (LIF) to a higher frequency for final transmission. Specifically, it is common in the United States to convert a signal at a LIF of 44 MHZ to a frequency division multiplex (FDM) final transmission frequency in the range of 53 MHZ to 857 MHZ. Similarly, European television transmission often utilizes up conversion of a signal at a LIF of 36.125 MHZ to a FDM final transmission frequency which may vary from a few tens of MHZ to nearly 1 GHz.
However, due to the relatively close packing of the FDM frequency bands associated with the various transmission channels, upconverters used as described above in the television industry are required to have a spectrally pure output so that information is transmitted in the desired FDM channel, without producing interfering signals in other FDM channels. Meeting the specifications generally required in the television industry is often very difficult due to the relatively close channelization scheme, the typically broad range of spectrum translated between, the relatively high transmission power requirements, the typically large amount of information modulated in the signal, and the like. For example, although often not providing the final transmission signal, upconverters are often deployed in the system such that their output signal must have enough output power to pass through a number of passive splitters and combiners that are disposed in the signal path. Upconverters used in these applications are not only required to translate a signal from one frequency to another within tight tolerances, but must also amplify the signal to a specified relatively high level.
Accordingly, the television industry presently uses upconverters that are designed using mostly discrete components, i.e., transistors, inductors, capacitors, resisters, deployed on printed circuit boards to provide discrete mixers, such as may be relatively easily relied upon to accommodate the relatively high transmission powers, provide the sharp cutoff filters needed to remove unacceptable spurious signals, and operate throughout the desired frequency spread. However, the use of such components tends to result in an upconverter product which is large, expensive, and which consumes large amounts of power. For example, a typical state of the art upconverter providing head end quality for use in television transmission applications requires a 19 inch rack mount form factor. Such a size requirement significantly limits the situations in which the upconverter may be deployed. Moreover, the use of such discrete components generally results in relatively high power requirements, further limiting deployment opportunities.
Additional circuit limitations associated with the use of such discrete components further encumber the design and operation of prior art devices. For example, it is often very difficult and/or expensive to achieve good matching of components when utilizing discrete components. However, matching of components in order to implement particular circuit designs is often critical, e.g., as little as 1° of mismatch in certain circuit configurations introduce spurious signals that generally cannot be tolerated in the aforementioned television transmission applications. Accordingly, particular circuit designs are often precluded from use due to the difficulty and/or expense associated with suitably matching components to implement a circuit design.
Accordingly, a need exists in the art for a frequency translation function to be provided in a reduced form factor to reduce size, expense, and/or power consumption. A further need exists in the art to provide such frequency translation function in an integrated circuit or circuits to achieve the aforementioned reduced size, expense, and/or power consumption as well as to facilitate component matching and, therefore, broaden the circuit designs available for use in providing frequency translation functions.